Abstract
The important physical processes acting in shock waves in molecular clouds are discussed. The magnetic field plays an important role in determining the structure of a shock wave in molecular gas. Because of the low fractional ionization, the magnetic field lines, together with the electron-ion plasma, can “slip” through the neutral gas; this “magnetic-ion-slip” can result in shock structures which are qualitatively different from nonmagnetic shock waves. The molecular processes acting in shock waves are reviewed, with attention to molecular excitation and dissociation, and a few important chemical reaction channels. The infrared spectra of C-type shocks are discussed, and theoretical models are compared to observations (in the BN-KL region of the Orion Molecular Cloud) of emission lines from vibrationally and rot at ion ally-excited H2, and rotationally excited CO and OH. Theoretical shock modelling is currently hindered by uncertainties in various cross sections for collisional excitation; some of these uncertainties are pointed out in hopes of stimulating further theoretical or laboratory work.
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Draine, B.T. (1985). Theoretical Models of Shock Waves in Molecular Clouds. In: Diercksen, G.H.F., Huebner, W.F., Langhoff, P.W. (eds) Molecular Astrophysics. NATO ASI Series, vol 157. Springer, Dordrecht. https://doi.org/10.1007/978-94-009-5432-8_10
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